/*! normalize.css v3.0.3 | MIT License | github.com/necolas/normalize.css */

/**
 * 1. Set default font family to sans-serif.
 * 1. 设置默认字体样式为无衬线字体
 * 2. Prevent iOS and IE text size adjust after device orientation change,
 * 2. 防止IOS设备和IE下字体大小因为屏幕的转向而改变。
 *  附：iOS设备旋转后可能会自动调整字体大小（e.g. 竖着的时候是14px，横着就自动调整成20px）。
 * without disabling user zoom.
 * 并没有禁用用户放大。
 */

html {
    font-family: sans-serif; /* 1 */
    -ms-text-size-adjust: 100%; /* 2 */
    -webkit-text-size-adjust: 100%; /* 2 */
}

/**
 * Remove default margin.
 * 移除默认的margin.
 */

body {
    margin: 0;
}

/* HTML5 display definitions
   ========================================================================== */

/**
 * Correct `block` display not defined for any HTML5 element in IE 8/9.
 * 纠正了HTML5元素的块状属性在IE8/9中无法识别。
 * Correct `block` display not defined for `details` or `summary` in IE 10/11
 * and Firefox.
 *IE10/11及Firefox中details` or `summary无法块状显示
 * Correct `block` display not defined for `main` in IE 11.
 *在IE11中main不是块状级别。
 */

article,
aside,
details,
figcaption,
figure,
footer,
header,
main,
menu,
nav,
section,
summary {
    display: block;
}

/**
 * 1. Correct `inline-block` display not defined in IE 8/9.
 * 1.补充了HTML5新元素inline-block在IE8/9下的正确显示。
 * 2. Normalize vertical alignment of `progress` in Chrome, Firefox, and Opera.
 * 2.补充了部分HTML5新元素在浏览器下的垂直对齐方式为基线对齐（vertical-align: baseline）
 */

audio,
canvas,
progress,
video {
    display: inline-block; /* 1 */
    vertical-align: baseline; /* 2 */
}

/**
 * Prevent displaying `audio` without controls in Mobile Safari 4/5/6/7.
 *如果audio标签没有控制栏，则应该隐藏
 */

audio:not([controls]) {
    display: none;
    height: 0;
}

/**
 * Address `[hidden]` styling not present in IE 8/9/10.
 * Hide the `template` element in IE 8/9/10/11, Safari, and Firefox < 22.
 * 新的template标签用于HTML模板，兼容旧浏览器，隐藏模板。
 */

[hidden],
template {
    display: none;
}

/* Links
   ========================================================================== */

/**
 * Remove the gray background color from active links in IE 10.
 * 移除在IE10下点击超链接出现的背景。
 */

a {
    background-color: transparent;
}

/**
 * Improve readability of focused elements when they are also in an
 * active/hover state.
 */

a:active,
a:hover {
    outline: 0;
}

/* Text-level semantics
/**
*
*语义化文本标签
*/
/*
   ========================================================================== */

/**
 * Address inconsistent styling of `abbr[title]`.
 * 1. Correct styling in Firefox 39 and Opera 12.
 * 2. Correct missing styling in Chrome, Edge, IE, Opera, and Safari.
 */

abbr[title] {
    border-bottom: none; /* 1 */
    text-decoration: underline; /* 2 */
    text-decoration: underline dotted; /* 2 */
}

/**
 * Address inconsistent styling of b and strong.
 * 1. Correct duplicate application of `bolder` in Safari 6.0.2.
 * 2. Correct style set to `bold` in Edge 12+, Safari 6.2+, and Chrome 18+.
 */
/**
 *统一了b,strong样式格式：
 *1.abbr元素在firefox外其他的浏览器下没有下划线的问题
 *2.统一了Safari and Chrome 给b 和strong设置的属性是bolder
 */

b,
strong {
    font-weight: inherit; /* 1 */
}

b,
strong {
    font-weight: bolder; /* 2 */
}

/**
 * Address styling not present in Safari and Chrome.
 */
/**
*dfn用于对特殊术语和专业短语的定义，在safari和chrome中不是斜体
*
*/

dfn {
    font-style: italic;
}

/**
 * Address variable `h1` font-size and margin within `section` and `article`
 * contexts in Firefox 4+, Safari, and Chrome.
 */

/**
*在section和article中h1标签的字体大小、margin样式不统一
*
*/

h1 {
    font-size: 2em;
    margin: 0.67em 0;
}

/**
 * Address styling not present in IE 8/9.
 */
/**
*mark标签用来突出显示标记的文本，背后有一个高亮的背景色，低版本中并不识别。
*
*/


mark {
    background-color: #ff0;
    color: #000;
}

/**
 * Address inconsistent and variable font size in all browsers.
 */
/**
 *统一了small标签在所有浏览器中的样式
 *
 */
small {
    font-size: 80%;
}

/**
 * Prevent `sub` and `sup` affecting `line-height` in all browsers.
 */
/**
 *sub和sup表示上标和下表，统一两者的样式。
 *
 */
sub,
sup {
    font-size: 75%;
    line-height: 0;
    position: relative;
    vertical-align: baseline;
}

sup {
    top: -0.5em;
}

sub {
    bottom: -0.25em;
}

/* Embedded content
   ========================================================================== */

/**
 * Remove border when inside `a` element in IE 8/9/10.
 */
/**
 * 移除了在IE 8/9/10下a标签img的边框(旧版本的IE浏览器下有蓝色边框)
 */
img {
    border: 0;
}

/**
 * Correct overflow not hidden in IE 9/10/11.
 */
/**
* 图片多余部分在IE 9/10/11下不隐藏的问题
*/

svg:not(:root) {
    overflow: hidden;
}

/* Grouping content群组元素
   ========================================================================== */

/**
 * 修复margin不起作用问题
 */

figure {
    margin: 1em 40px;
}

/**
 * Address inconsistent styling of `hr`.
 * 1. Correct `box-sizing` set to `border-box` in Firefox.
 * 2. Correct `overflow` set to `hidden` in IE 8/9/10/11 and Edge 12.
 */
/**
* 统一了hr样式.
* 1. 在Firefox下设置了box-sizing`为border-box
* 2. 修正在IE 8/9/10/11 and Edge 12下overflow值为visible
*/

hr {
    box-sizing: content-box; /* 1 */
    height: 0; /* 1 */
    overflow: visible; /* 2 */
}

/**
 * Contain overflow in all browsers.
 */
/**
* 原先标签多出的直接溢出，这里标签溢出增加滚动条.
*/

pre {
    overflow: auto;
}

/**
 * 1. Correct inheritance and scaling of font-size for preformatted text.
 * 2. Address odd `em`-unit font size rendering in all browsers.
 */
/**
* 统一了在各个浏览器中字体样式
*
*/

code,
kbd,
pre,
samp {
    font-family: monospace, monospace; /* 1 */
    font-size: 1em; /* 2 */
}

/* Forms表单
   ========================================================================== */

/**
 * Known limitation: by default, Chrome and Safari on OS X allow very limited
 * styling of `select`, unless a `border` property is set.
 */

/**
 * 1. Correct font properties not being inherited.
 * 2. Address margins set differently in Firefox 4+, Safari, and Chrome.
 */
/**
* 纠正了表单标签字体不继承的问题。
* 在各个浏览器中外边距不统一
*/

button,
input,
optgroup,
select,
textarea {
    font: inherit; /* 1 */
    margin: 0; /* 2 */
}

/**
 * Address `overflow` set to `hidden` in IE 8/9/10/11.
 */
/**
* 将button便签在IE 8/9/10/11溢出属性改为visible
*/

button {
    overflow: visible;
}

/**
 * Address inconsistent `text-transform` inheritance for `button` and `select`.
 * All other form control elements do not inherit `text-transform` values.
 * Correct `button` style inheritance in Firefox, IE 8/9/10/11, and Opera.
 * Correct `select` style inheritance in Firefox.
 */
/**
* 纠正了button、select标签text-transform属性继承的问题。
*
*/
button,
select {
    text-transform: none;
}

/**
 * 1. Avoid the WebKit bug in Android 4.0.* where (2) destroys native `audio`
 *    and `video` controls.
 * 2. Correct inability to style clickable `input` types in iOS.
 * 3. Improve usability and consistency of cursor style between image-type
 *    `input` and others.
 */
/**
* 1. 避免Android 4.0.*中的WebKit bug破坏原生的audio和video控制器.
* 2. 无法设置可点击的input标签问题
* 3. 统一其他类型的input光标样式
*
*/

button,
html input[type="button"], /* 1 */
input[type="reset"],
input[type="submit"] {
    -webkit-appearance: button; /* 2 */
    cursor: pointer; /* 3 */
}

/**
 * 统一按钮禁用时的鼠标光标样式
 */

button[disabled],
html input[disabled] {
    cursor: default;
}

/**
 * 移除Firefox 4+下的边框和内边距.
 */

button::-moz-focus-inner,
input::-moz-focus-inner {
    border: 0;
    padding: 0;
}

/**
 * Restore focus style in Firefox 4+ (unset by a rule above)
 */

button:-moz-focusring,
input:-moz-focusring {
    outline: 1px dotted ButtonText;
}

/**
 * 修复了Firefox 4+中设置`line-height`为normal!important样式。
 *
 */

input {
    line-height: normal;
}

/**
 * It's recommended that you don't attempt to style these elements.
 * Firefox's implementation doesn't respect box-sizing, padding, or width.
 *
 * 1. Address box sizing set to `content-box` in IE 8/9/10.
 * 2. Remove excess padding in IE 8/9/10.
 */
/**
* 1. 修正checkbox、radio在IE 8/9/10下box sizing设置为content-box的问题
* 2. 移除checkbox、radio在IE 8/9/10中多余的内边距
*/

input[type="checkbox"],
input[type="radio"] {
    box-sizing: border-box; /* 1 */
    padding: 0; /* 2 */
}

/**
 * Fix the cursor style for Chrome's increment/decrement buttons. For certain
 * `font-size` values of the `input`, it causes the cursor style of the
 * decrement button to change from `default` to `text`.
 */
/*修正input[type="number"]光标改变效果*/


input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button {
    height: auto;
}

/**
 * Address `appearance` set to `searchfield` in Safari and Chrome.
 */
/*修正在chrome下input[type="search"]appearance值设置为searchfield*/

input[type="search"] {
    -webkit-appearance: textfield;
}

/**
 * Remove inner padding and search cancel button in Safari and Chrome on OS X.
 * Safari (but not Chrome) clips the cancel button when the search input has
 * padding (and `textfield` appearance).
 */
/**
* 统一输入框的样式，移除了默认的一些样式。
*/

input[type="search"]::-webkit-search-cancel-button,
input[type="search"]::-webkit-search-decoration {
    -webkit-appearance: none;
}

/**
 * 统一了fieldset的border、外边距和内边距
 */

fieldset {
    border: 1px solid #c0c0c0;
    margin: 0 2px;
    padding: 0.35em 0.625em 0.75em;
}

/**
 * 1. Correct `color` not being inherited in IE 8/9/10/11.
 * 2. Remove padding so people aren't caught out if they zero out fieldsets.
 */
/**
* 1. 在 IE 8/9/10/11下颜色不继承问题
* 2. 重置了内边距
*/

legend {
    border: 0; /* 1 */
    padding: 0; /* 2 */
}

/**
 * Remove default vertical scrollbar in IE 8/9/10/11.
 */
/**
* 移除了textarea在IE 8/9/10/11下的滚动条
*/

textarea {
    overflow: auto;
}

/**
 * Restore font weight (unset by a rule above).
 * NOTE: the default cannot safely be changed in Chrome and Safari on OS X.
 */
/**
* 统一了optgroup标签的font-weight属性为bold
*
*/

optgroup {
    font-weight: bold;
}
